The present invention relates to the field of robotic and computer assisted surgery, and more specifically to equipments and methods for robotic and computer assisted microsurgery.
As shown in U.S. Pat. No. 5,943,914 to Morimoto et al., “Master/slave” robots are known in which a surgeon's hand input is converted to a robotic movement. This is particularly useful for motion scaling wherein a larger motion in millimeters or centimeters by the surgeon's input is scaled into a smaller micron movement. Motion scaling has also been applied in cardiac endoscopy, and neurosurgical target acquisition brain biopsy (with a needle) but only in one degree of freedom, for example only for insertion, not for a full range of natural hand movement directions, i.e., not for all possible degrees of natural motion, Cartesian, spherical or polar coordinate systems or other coordinate systems.
Further, in the prior art, surgical robots have been purposefully designed to eliminate the natural hand tremor motions of a surgeon's hand which is about a 50 micron tremor which oscillates with some regularity. The common presumption is that tremor motion creates inaccuracies in surgery. Therefore, robots have been tested which entirely eliminate the surgeon's natural hand tremor. See “A Steady-Hand Robotic System for Microsurgical Augmentation” Taylor et al., International Journal Of Robotics Research, 18(12):1201-1210 December 199, and also see “Robotic-assisted Microsurgery: A Feasibility Study in the Rat” LeRoux et al., Neurosurgery, March 2001, Volume 48, Number 3, page 584
The way the primate body handles proprioceptive perception is via sensory feedback scaling (up and down) at the muscular level through the intrafusal fiber system of the Gamma efferent neural circuit. This system responds dynamically to changes in the anticipated muscle performance requirement at any instance by adjusting muscle tone with increased discharging for arousal and attention focusing states, and decrease output for resting and low attention states. The muscle spindle apparatus that does this is located in the muscle body, therefore feedback sensory scaling for muscle positioning, force, length and acceleration is partly programmed at the effector level in “hardware” of the body, i.e., the muscle itself. The evidence indicates a 10 cycle per second refresh rate for the human neurophysiological system in general.
Joint position and fine motor function of the fingers occurs through unidirectional (50% of fibers) and bi-directional (50% of fibers) sensing at the joint structure. This coding is for rotation about an axis, but not for force and no clear speed of rotation feedback.
Cutaneous receptors in the skin code for motion, by modulating higher centers in the thalamus and cerebral cortex. This can be timed to about 75 ms delays before motion occurs, three neuronal synaptic transmission delays. These sensors are primarily distal to the joint of rotation and distal in the moving effector limb. Finally, the sense of contact is totally discrete from the above motion feedback sensory systems and the neural pathways and integration centers in the deep hemispheres and cerebral cortices function independent of motion to a large degree.
Force reflectance sensing is also known in order to provide tactile or haptic feedback to a surgeon via an interface. See “Connecting Haptic Interface with a Robot” Bardofer et al., Melecon 200-10th Mediterranean Electrotechnical Conference, May 29-31 2000, Cyprus.
However, in testing, all of these techniques ultimately slow down the actual surgery especially when performed in conjunction with a microscope for viewing the operation. The procedure time is typically increased by two to three times. See Robotic-assisted Microsurgery: A Feasibility Study in the Rat” cited above. It is believed that this affect is related to dissonance between a surgeons expectations and the feedback and motions of a surgical robot in use.
Another major design issue regards the choice between locating the surgeon in his normal operating position adjacent to the surgical field or locating the surgeon more remotely from the normal operating position at a terminal with a joystick and viewing screen for example. The prior art elects to locate the surgeon remotely from the traditional operational position about the head and to use monitors to display the operation to the surgeon.